Deep Stops Increases DCS

[UWSojourner]

Someone (Kevin) correct me if I'm wrong here....but I think Ross H is reading the heat maps wrong. The heat maps compare two profiles, compartment-by-compartment. You can't compare two compartments in the same profile on the one heatmap directly. So pointing out that "Cell 9" is the controlling one and that Kevin's heat map shows Cell11 as the highest isn't a correction. Kevin's heat map is showing that Cell 11 is more saturated in VPM-B than in Buhlmann....not that Cell 11 is more saturated than Cell 9.

That's correct Victor. The heat maps are not trying to compare different compartments in one profile. The maps compare supersaturation patterns between profiles. As I've stated elsewhere, they are comparative only and, at a glance, visually show relative similarities in how each profile treats supersaturation. That's all they were designed to do.

 

[PfcAJ]

But the stops were very different than a VPM profile, 29 minutes at 70 and 60 feet for the NEDU deep stop profile vs. 14 minutes at 90, 80, 70 and 60 feet for VPM+3, just as an example. Like I said, the NEDU profiles do not look similar to VPM or Buhlmann profiles for the 30 min air dive to 170 feet.

That's fine. The nedu study didn't test any of those profiles you ran.

Ross is trying to argue that the nedu study didn't test deep stops and that whatever dcs came about wasn't a result of the stop distraction. This is unequivocally false.

 

[rossh]

4/ Absolute rubbish - the wishful thinking continues. Nedu did not push the dives, there is almost NO supersaturation present in both profiles. Hard to make DCS with no profile stress.
.

And yet there was dcs and more of it on the profile with a [x] EXTENDED TIME SHALLOW stop distribution.

Yes, quite a conundrum. No real profile stress present in either profile. Two varieties of shallows stops, I wonder what other kind of stress was elevated?

Ross is trying to argue that the nedu study didn't test deep stops and that whatever dcs came about wasn't a result of the stop distraction. This is unequivocally false.

FACT - The nedu did not test tech level, VPM-B ,or other kind of deep stop.

FACT - The nedu tested two kinds of shallow stops.

Stop trying to con us into thinking otherwise!



We need not be concerned with "shallow model problems". No one here does these.

However the solution is already built into ZHL / VPM-B with the Haldane Schriener equations, and works just fine in both.

VPM-B is the Green part. Big pink part is the Nedu test. Not the same thing.

 

[scubadada]

The American Statistical Society has warned against p-value testing to choose between hypotheses.

An Error Occurred Setting Your User Cookie

Interesting policy statement. However, as stated in the article, most everyone has been taught p-value testing. The biggest problem is probably the application of statistics by people who don't know how to do statistics.

When I first read the NEDU article, it struck me as odd that they used a one-sided Fisher's exact test, I probably would have chosen a two-sided test. I ran a 2x2 contingency table and got a p of 0.087 using a two-sided test and a p of 0.049 using a one-sided test. The NEDU study states a p of 0.47. This is not rocket science, the results are not significant using a two-tailed test and are right on the border using a one-tailed test. Statistical significance was nearly lost with exclusion of one episode of DCS in the deep stops group.

 

[EFX]

I suspected that was the case. And that's ok. This is just my opinion, but the fact that you can summarily dismiss several studies of actual dives by researchers, some tasked with keeping their country's divers safe, in preference for "anecdotal evidence" says a lot. Mostly it tells me that no matter what evidence is offered, some will not be convinced.

I'm not dismissing the dives because of their validity (or lack of it) but because I don't know the details. So how can I say either way whether the study is valid or not in regards to sport diving, other than taking your word for it. However, the NEDU test I did study and this is important -- I dismiss its generalized conclusions that for many SB's readers are interpreting that deep stops are inferior to shallower dive profiles or B-GF is safer than VPM-B.

I'm not saying that anecdotal stories should replace scientific studies, but only that such stories indicate that deep stops and bubble models indicate safer dives in contrast to some SB's assumptions which are based on a biased view of the NEDU evidence. You're right. I won't be convinced by evidence from a study that has no application to sport diving.

 

[PfcAJ]

Yes, quite a conundrum. No real profile stress present in either profile. Two varieties of shallows stops, I wonder what other kind of stress was elevated?







FACT - The nedu did not test tech level, VPM-B ,or other kind of deep stop.

FACT - The nedu tested two kinds of shallow stops.

Stop trying to con us into thinking otherwise!



We need not be concerned with "shallow model problems". No one here does these.

However the solution is already built into ZHL / VPM-B with the Haldane Schriener equations, and works just fine in both.

VPM-B is the Green part. Big pink part is the Nedu test. Not the same thing.

Ross, what was the average depth of the two profiles? Which one had a higher incidence of DCS?

Spoiler alert: the deeper average

 

[JohnnyC]

The plural of anecdote isn't data......

 

[EFX]

But your reference to "hidden agendas" is a little Rossonian and bizarre.

I didn't want to imply that the Navy is somehow dishonest or devious in their publication of the NEDU study. I was thinking of covert missions that could not be disclosed but would be relevant to their deep stop study.

 

[EFX]

Ross is trying to argue that the nedu study didn't test deep stops and that whatever dcs came about wasn't a result of the stop distraction. This is unequivocally false.

No. Ross isn't arguing what you say above. He and I are arguing that the deep stops the NEDU study used are fundamentally different from sport bubble models. So different, in fact, that from the perspective of VPM or RGBM they should be called long shallow stops.

 

[KevinNM]

No. Ross isn't arguing what you say above. He and I are arguing that the deep stops the NEDU study used are fundamentally different from sport bubble models. So different, in fact, that from the perspective of VPM or RGBM they should be called long shallow stops.

I'm trying to understand your position. I think the arument you are making is that if they had done less deco and done it deeper they would have bent less divers? Does doing overly long deco typically bend divers? Do you expect to get a higher percentage of bent divers if you did 30 minutes at 20 feet vs 10 minutes at 20 feet that the dive table called for?